Tumors of the perianal area in dogs can be very common, being mainly of three types: one benign called perianal adenoma, which primarily affects unneutered male dogs; and two malignant ones, adenocarcinoma of the anal sacs and perianal adenocarcinoma, with a high probability of metastasis and paraneoplastic syndrome with hypercalcaemia.
The associated clinical signs are those derived from the growth of a mass in a sensitive area of dogs, which begin to lick, crawl and self-mutilate, which begins to bleed, hurt and cause discomfort and secondary infections that cause fever and may fistulate. Diagnosis is achieved with cytology and biopsy and treatment will be surgical and medical. In this article on our site we address the topic of perianal tumor in dogs, its symptoms and treatment
Types of perianal tumors in dogs
In the perianal area, extending between the anus and the genitals of the dog, pathologies such as tumors may occur. It is a very well innervated and irrigated area, so pain and sensitivity during manipulation are very high.
Around the year we find two structures:
- Anal sacs: Diverticula of the blind fundus on each side of the anus, between the external and internal anal sphincter. Its function is to accumulate viscous and serous and foul-smelling liquid that is synthesized by internal glands and that is eliminated naturally during defecation in dogs. It is useful in recognition between dogs and is also released in stressful situations.
- Perianal glands: Also called circumanal or hepatoid glands, which have hormone receptors (androgens, estrogens, and growth hormone). They are located in the subcutaneous tissue surrounding the dog's anus. These are sebaceous-type glands that do not secrete content.
Different types of tumors can appear in the perineal area, the most common being the following:
- Perianal adenoma: a mass is observed at the base of the tail or in the perianal area with progressive and non-painful growth. Sometimes it can ulcerate. It occurs more frequently in older non-castrated males, being the most prevalent tumor in them. However, it is also seen in females, especially in sterilized ones. It is a benign process.
- Perianal adenocarcinoma: it is also a tumor of the perianal glands with the same characteristics as the previous one, but malignant and, therefore, with greater aggressiveness. It can be given at any age and in any sex.
- Anal sac adenocarcinoma: This is the most common tumor in spayed and non-spayed females and in older dogs. Hypercalcemia (increased calcium in the blood) occurs in this tumor.
It should be noted that there is a certain racial predisposition to the development of perianal tumors, being more frequent in:
- Cocker spaniel.
- Fox terrier.
- Races of Nordic origin.
- Large breeds, may be associated with testicular tumor.
Perianal Tumor Symptoms in Dogs
In perianal adenomas, dogs initially show neither pain nor associated symptoms. Over time, and if they become infected, they can present fever, malaise and anorexia If the size is very large, they can present colorectal obstruction and perineal pain, causing defecation is a very difficult and painful process for the dog.
perianal adenocarcinomas are more aggressive, and clinical signs may appear such as loss of appetite, pain and lethargyThey are highly likely to produce hypercalcaemia as part of the paraneoplastic syndrome (set of symptoms associated with tumors), as well as clinical signs derived from the damage caused by this increase in calcium in the kidneys, such as polyuria/polydipsia syndrome (urinate and drink more than usual).
In adenocarcinomas of the anal sacs this paraneoplastic syndrome can also occur, but to a lesser extent (around 25-50 % of the dogs).
In summary, in perianal tumors dogs can manifest the following symptomatology:
- Perianal pain.
- Bad odor in the perianal region.
- Insistent licking of the area.
- Tumor bleeding.
- Drag of the rear area of the dog.
- Ulceration.
- Secondary infections.
- Anal itch.
- Anorexy.
- Polyuria.
- Polydipsia.
- Lethargy.
- Apathy.
- Fever.
- Fistulas.
- Inappetence.
- Weightloss.
- Colorectal obstruction.
- Constipation.
- Hematochezia (blood in stool).
- Pain on defecation (dyschezia).
- Difficult defecation (tenesmus).
These tumors have a high capacity to metastasize, first invading the regional lymph nodes (inguinal and pelvic) and later the internal organs.
Diagnosis of perianal tumor in dogs
In case of suspicion of a malignant tumor, diagnosis imaging techniquesshould be performed in order to look for metastases, since the 50 to 80% of cases of perianal tumors have metastases at the time of diagnosis. The techniques used are abdominal ultrasound to assess the lymph nodes and other organs such as the kidneys or liver, while radiography is useful to visualize the thoracic organs, especially the lungs.
In the blood analysis hypercalcaemia and kidney damage can be observed in adenocarcinomas.
Canine perianal tumor treatment
The treatment of perianal tumors in dogs is surgical removal. However, depending on the type of tumor and whether or not there is metastasis, treatment may vary:
- In the case of perianal adenomas, as they are so closely related to the hormones of non-castrated males, they should be castration to reduce the risk of future recurrences, reducing it by 90%.
- When there are metastases or tumors are malignant, complete removal with surgical margins should be performed and treatment with chemotherapy and radiotherapy.
- In cases of renal function damage and hypercalcaemia, specific treatment with fluid therapy and drugs should be applied before surgery to reduce anesthetic risk.
- When the size of the lymph nodes makes defecation difficult, they should be removed to facilitate the process.
In any case, it is essential to go to the veterinary clinic so that a specialist can diagnose the type of tumor and decide on the best treatment.
